Article
Thermodynamics
Jinguo Sun, Yihua Ren, Yong Tang, Shuiqing Li
Summary: This study investigates the extinction characteristics of premixed stagnation flames (PSFs) under different conditions and the impact of flame stability by air flow pulsations. Through experiments and numerical simulations, it is revealed that wall heat flux and air pulsations have significant effects on the extinction stretch rate and flame stability in PSFs.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Engineering, Electrical & Electronic
Rafal Sylwester Kasikowski, Boguslaw Wiecek
Summary: The fringing-field phenomenon in magnetic components with an air gap can cause localized heating in windings and reduce power conversion efficiency, which can be analyzed using infrared thermography. Thermographic analysis and power loss measurements for different air gap configurations can be used to construct compact thermal models of the inductor. Splitting a single air gap into multiple individual air gaps can significantly diminish the fringing effect.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Thermodynamics
Sanjeev Kumar Manjhi, Rakesh Kumar
Summary: This study focused on measuring surface heat flux on a flat plate at different angles of attack using coaxial thermocouples, and the results confirmed the capability of these in-house fabricated coaxial thermocouples to measure surface heat flux at different locations on aerodynamic vehicles.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2022)
Article
Thermodynamics
Kevin Nordin-Bates, Niklas Zettervall, Tomas Hurtig, Hanna Sundberg, Christer Fureby
Summary: This study focuses on the numerical modeling of sub-breakdown microwave-enhanced combustion in one-dimensional laminar methane-air flames. The effects of uniform microwave fields on flame speed, temperature, and composition are investigated. A model for the non-thermal plasma generated by the microwave field is constructed, and various methane-air kinetics schemes are used to compute laminar flame profiles under different microwave field strengths and stoichiometries. The study reveals the mechanisms behind the flame-speed increase at sub-breakdown electric field strengths and aims to develop simplified models suitable for large-scale numerical simulations.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
M. N. Sadiq, B. Sarwar, M. Sajid, N. Ali
Summary: This study investigates heat transfer for the stagnation point flow of micro-polar fluid in unsteady flow, using the Cattaneo-Christov heat flux model and numerical integration procedures. The analysis shows the effects of thermal relaxation time on temperature profiles, which decrease for larger relaxation times and increase with increasing Eckert number.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2022)
Article
Energy & Fuels
Marco Lubrano Lavadera, Christian Brackmann, Gianluca Capriolo, Torsten Methling, Alexander A. Konnov
Summary: Experimental results on the adiabatic laminar burning velocities and post-flame NO mole fractions of neat and blended ethanol and n-heptane premixed flames demonstrate that the addition of ethanol increases the burning velocity and reduces NO formation. These findings are crucial for the development and optimization of chemical kinetic models.
Article
Thermodynamics
M. B. Raida, G. J. Hoetmer, A. . A. . Konnov, J. A. van Oijen, L. P. H. de Goey
Summary: A new setup for burning velocity measurements using the Heat Flux method has been constructed, with improved burner design. The experimental results have high accuracy and good agreement with literature data.
COMBUSTION AND FLAME
(2021)
Article
Energy & Fuels
Tao Shu, Yuan Xue, Zijun Zhou, Zhuyin Ren
Summary: Experimental investigation of flame properties in ammonia/methane/air mixtures shows significant influence of gas composition and pressure on flame speeds and flammability limits. Linear correlation between flame speed and methane volume fraction is observed, with accurate prediction using Okafor et al. mechanism.
Article
Thermodynamics
Sanghoon Lee, Yosheph Yang, Jae Gang Kim
Summary: The Fay and Riddell (F-R) formula, widely used for estimating the stagnation-point heat flux on noncatalytic and fully catalytic surfaces, was found to underestimate noncatalytic heat flux due to the chemical composition at the surface. However, for fully catalytic heat flux, the F-R formula provides similar results to thermochemical nonequilibrium calculations, but overestimates the diffusive heat flux. Comparison with flight experimental data showed that the F-R formula overestimated the fully catalytic heat flux with an error of up to 50%.
INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW
(2023)
Article
Thermodynamics
Iskandar Waini, Anuar Ishak, Ioan Pop
Summary: This study investigates the impinging flow on a shrinking cylinder in Al2O3-Cu/water hybrid nanofluid subjected to prescribed surface heat flux. Two solutions are possible for the shrinking case, where one is stable in the long run. Friction and heat transfer on the surface increase with higher values of φhnfand γ.
INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW
(2021)
Article
Computer Science, Interdisciplinary Applications
Bharat Keshari Swain, G. C. Dash
Summary: In this analysis, the stability of MHD stagnation point flow and heat transfer of an electrically conducting viscous incompressible fluid on a horizontally stretching/shrinking permeable cylinder with volumetric heat source are investigated. The solution of the boundary value problems (BVP) is carried out with MATLAB's inbuilt solver bvp4c. The most significant findings are recorded as: an increase in magnetic field strength increases the skin friction at the solid surface which is consistent with progressive thinning of boundary layer, and there is a point of neutrality of thermal energy distribution during the high fluctuation of temperature irrespective of the presence of heat generation or absorption.
INTERNATIONAL JOURNAL OF MODERN PHYSICS C
(2023)
Article
Engineering, Aerospace
Ri Wang, Fengfei Lou, Bin Qi, A. Rong, Yuanye Zhou, Sujun Dong
Summary: In this paper, a subsonic high-temperature combustion gas heating (SHCH) test device is used to conduct experiments on the heat flux simulation of subsonic high-temperature combustion gas in the stagnation point region of a hypersonic vehicle. A Kriging surrogate model is proposed to determine the combustion gas temperature, and the heating capacity of SHCH and the feasibility of hypersonic aerothermal simulation testing are verified through comparisons and analysis of experimental and numerical simulation results.
Article
Chemistry, Physical
Ethan S. Hecht, Bikram Roy Chowdhury
Summary: The study measured the visible flame length and heat-flux characteristics of cryogenic hydrogen flames released from high-aspect ratio nozzles, finding that the aspect ratio of the release does not significantly affect the flame length or heat flux.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Thermodynamics
Jiawei Lai, Umair Ahmed, Markus Klein, Nilanjan Chakraborty
Summary: A Direct Numerical Simulation (DNS) database was used to compare the head-on quenching of stoichiometric methane-air and hydrogen-air flames, showing that the heat release rate and quenching distance are smaller for the stoichiometric hydrogen-air flame, especially under turbulent conditions. Well-known closures for the Flame Surface Density (FSD) or scalar dissipation rate (SDR) fail to accurately predict the mean reaction rate in the near-wall region, but recently proposed DNS-based corrections perform well for both fuels.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Chemistry, Physical
Yilong Yin, Paul R. Medwell, Bassam B. Dally
Summary: The low radiant intensity of hydrogen flames can be increased by adding biofuels with a high propensity for sooting. This study investigates the effects of biofuel concentration and phase on the combustion characteristics of turbulent nonpremixed hydrogen-based flames. Blending biofuel surrogates and hydrogen can enhance the formation of soot and increase luminosity, while also increasing NOx emissions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Dominik Schroeder, Kai Banke, Sebastian A. Kaiser, Burak Atakan
Summary: Fuel-rich combustion of methane with additives such as DME and ozone in an HCCI engine can produce work, heat, and useful chemicals. Experimental results show that ozone is a suitable additive for fuel-rich HCCI, reducing the fuel-fraction of DME needed. The mechanism of ignition differs between fuel-rich and fuel-lean combustion, with ozone showing potential for improving the economics of polygeneration processes.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
D. Kaczmarek, S. Shaqiri, B. Atakan, T. Kasper
Summary: Methane oxidation exhibits negative temperature coefficient behavior under high pressure and fuel-rich conditions. Reliable kinetic models and reaction path analysis are essential for designing polygeneration processes. The competition between oxidation and recombination pathways plays a key role in the observed NTC region.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
Charlotte Rudolph, Burak Atakan
Summary: A novel method for energy conversion in piston engines, pyrolysis of natural gas/hydrogen mixtures for energy storage, is investigated. The addition of hydrogen allows for increased yields of certain products but also reduces storage power and efficiency.
Article
Energy & Fuels
Simon Drost, Dennis Kaczmarek, Sven Eckart, Juergen Herzler, Robert Schiessl, Chris Fritsche, Mustapha Fikri, Burak Atakan, Tina Kasper, Hartmut Krause, Christof Schulz, Ulrich Maas
Summary: This study investigates the combustion characteristics of ethanol/air mixtures through experiments and simulations. The simplified reaction mechanism demonstrates performance close to the detailed mechanism. Within certain temperature and pressure ranges, the simplified mechanism shows good predictive capabilities for experimental data and laminar burning velocities.
Article
Thermodynamics
S. Lau, M. Gonchikzhapov, A. Paletsky, A. Shmakov, O. Korobeinichev, T. Kasper, B. Atakan
Summary: This study investigates the thermal behavior of aluminum diethylphosphinate (AlPi) as a flame retardant in ultra-high molecular weight polyethylene (UHMWPE). The research focuses on the effect of the flame retardant on the gas phase activity during polymer pyrolysis or combustion. The study finds that a small amount of AlPi significantly decreases the gas temperature in the flame, indicating its flame retardant effect.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Charlotte Rudolph, Dominik Freund, Dennis Kaczmarek, Burak Atakan
Summary: This study investigates the conversion of chemical plant waste gases into fuel for carbon recovery and simultaneous output of work and heat. Experimental results show that under appropriate conditions of oxygen addition and equivalence ratio, the conversion rate of ammonia in the waste gases can be improved, and high energy efficiency can be achieved.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Julian Quenel, Burak Atakan
Summary: The influence of fin geometries, PCM thermal conductivity, and discharge temperature of the secondary fluid on thermal energy storage systems were investigated. The study found that the improvement methods increased the heat flux, but to a lesser extent than expected. The impact of thermal conductivity was found to be lower at higher fin volume fractions. Increasing the discharge temperature difference had the strongest impact on heat flux but also increased exergy loss.
HEAT AND MASS TRANSFER
(2022)
Article
Materials Science, Multidisciplinary
Sebastian Grimm, Seung-Jin Baik, Patrick Hemberger, Tina Kasper, Andreas M. Kempf, Burak Atakan
Summary: In this study, the thermal decomposition of Zr(acac)(4) was investigated in a SIC-microreactor on the microsecond time scale. Six important zirconium intermediates were identified in the gas phase for the first time using synchrotron radiation and photoelectron photoion coincidence spectroscopy. The flow field in the microreactor was numerically simulated, showing that helium provides a more uniform flow field than argon.
JOURNAL OF MATERIALS RESEARCH
(2022)
Article
Chemistry, Multidisciplinary
Sebastian Grimm, Patrick Hemberger, Tina Kasper, Burak Atakan
Summary: This study investigates the decomposition and reduction of ferrocene in the gas-phase. By detecting reactive intermediates and proposing a reaction mechanism, the underlying chemistry is understood. The addition of hydrogen is found to affect the product formation.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Thermodynamics
Tobias Guth, Burak Atakan
Summary: The refrigeration industry is challenged by the replacement of harmful refrigerants and the optimization of the refrigeration system operation for environmental protection. This study presents a semi-empirical model for a variable speed scroll compressor for R-290. The model calculates the refrigerant mass flow, discharge temperature, and power consumption based on physical laws and empirical efficiencies fitted by polynomials. The model shows good accuracy for the investigated operating points and demonstrates transferability to other compressors and refrigerants.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)
Article
Thermodynamics
Charlotte Rudolph, Claire M. Gregoire, Sean P. Cooper, Sulaiman A. Alturaifi, Olivier Mathieu, Eric L. Petersen, Burak Atakan
Summary: The need for fundamental research on the decomposition and formation of base chemicals under unusual operating conditions of natural-gas-fueled combustion engines is emphasized. This study investigates the CO formation during the pyrolysis of CO2/CH4 mixtures in engine-based dry methane reforming and tests the validity of literature reaction mechanisms. The results show competing reactions in the pyrolysis and oxidation pathways and the limited availability of H radicals, leading to reduced reactivity. Additionally, none of the tested mechanisms can accurately predict the time-resolved CO formation, highlighting the importance of validating detailed kinetics models under non-typical conditions.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Mohamed Elmnefi, Waqas Al-Khazraji
Summary: This study aims to enhance the thermal efficiency and reduce the cost of parabolic trough solar collectors (PTSC) by investigating the effects of different operating conditions. A novel configuration using a noncirculated nanofluid was designed to absorb solar radiation. Computational fluid dynamics simulations and experimental tests were conducted to compare the performance of single and triple copper tube models. The findings showed that the single copper tube model had superior performance and achieved a maximum thermal efficiency of 55.31%.
INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW
(2023)
Article
Thermodynamics
Mohamed Elmnefi, Mohanad Al-Sammarraie
Summary: This study investigates the impact of adding Al2O3 and TiO2 nanoparticles to deionized water as a base fluid on the performance of a horizontal counterflow double-pipe heat exchanger under turbulent flow conditions. Experimental results show that the heat transfer rate and coefficients increased with increasing volume flow rate and nanofluid concentration. The Al2O3/water nanofluid outperformed the TiO2/water nanofluid and pure water in all tested properties.
HEAT TRANSFER RESEARCH
(2022)
Article
Thermodynamics
Mohamed Elmnefi, Raed Abdullah
Summary: Various enhancement techniques can significantly reduce energy consumption and increase power plant efficiency. Using nanofluids (TiO2/water and Al2O3/water) in shell-and-tube heat exchangers can improve heat transfer parameters, with Al2O3/water nanofluid showing higher performance than TiO2/water nanofluid and base fluid.
HEAT TRANSFER RESEARCH
(2021)
Article
Chemistry, Physical
Sebastian Grimm, Seung-Jin Baik, Patrick Hemberger, Andras Bodi, Andreas M. Kempf, Tina Kasper, Burak Atakan
Summary: In this study, the thermal decomposition of aluminium acetylacetonate was investigated in a microreactor using i(2)PEPICO between 325 and 1273 K. Quantum chemical calculations and CFD were used to characterize the reaction and flow field. Various decomposition products were identified, including aluminium bis(diketo)acetylacetonate-H and acetylacetone as the major initial products formed at temperatures above 600 K. The formation mechanism of gas-phase aromatic hydrocarbons was discussed and Arrhenius parameters were presented for the gas-phase decomposition kinetics.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)